1. Field of the Invention
The present invention relates to a channel-switching multicast distribution apparatus, a multicast reception apparatus, and a channel-switching multicast distribution method.
Priority is claimed on Japanese Patent Application No. 2006-191462, filed Jul. 12, 2006, the content of which is incorporated herein by reference.
2. Description of the Related Art
Due to recent improvement of broadband communication networks, a demand for distributing large amounts of video content via IP (Internet protocol) networks has been increased. In such video-content distribution services, when distribution time is predetermined, the same video content can be efficiently and simultaneously distributed to a large number of audiences. For example, a telecast using the Internet (called “Internet protocol television (IPTV)” below) provides a service of simultaneously distributing a plurality of TV programs through a plurality of channels, in accordance with a TV program table (i.e., similar to distribution using broadcast waves). More specifically, different multicast addresses are assigned to the plurality of channels, so as to form a multicast group corresponding to each of the channels. In this case, channel switching is performed by joining the multicast group of a new channel which the audience wants to watch. Accordingly, the audience can select any channel via an IPTV reception device, and watch programs of any channel by freely switching channels. When switching from the channel that the audience has been watching, whether to leave the multicast group of the channel is left to the audience's decision.
However, with respect to the channel switching, delay is generated in starting the reproduction of a program in the new channel, due to necessity of data storage into the IPTV reception device, or the like. For example, (i) storage of data for decoding a digital-compression-encoded video content, (ii) storage of data for decoding error-correction codes which are used for correcting transmission errors, (iii) reproductive buffering for correcting a fluctuation in data-arrival intervals, or the like, requires a lot of time. The following Patent Documents 1 and 2 disclose channel switching techniques for executing quick channel switching.    Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2004-80785.    Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2005-124193.
However, in the above-described known channel switching techniques, the channel switching server responds individually to each channel switching request (from each audience) for selecting a new channel, and video data is sent by unicast. Therefore, an individual data sending process for channel switching (requested by each audience) should be performed. In this case, when a large number of audiences request the channel switching simultaneously, a large load is imposed on the channel switching server.
Also in the above-described known channel switching techniques, the audience must send a channel switching request for selecting a new channel to the channel switching server. Therefore, channel switching cannot be executed by a simple communication process of joining a new multicast group. Thus, the communication processing is complex.